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IV. — Originating Point And Cause Of The Explosion.
As to the indications of force as a guide to discovering the originating point of the explosion, there were practically no indications of force along the main road of the mine a short distance inbye and outbye side of the "friction-gear." The reason for the cessation of the explosion in these directions is not far to seek: there were wet areas of ground a short distance inbye and outbye side of the 3rd North way end, and there was therefore no supply of dust available to further propagate the explosive heat. Passing into the 3rd North it was found that for some distance the stoppings on either side of the intake were blown out to the right and left, but as the point was approached where No. 1 Brake joins the 3rd North main intake, thence inwards along the main road the stoppings are all blown in slanting and south-westerly directions and the indications of force point to the explosion having come down the "Brakes" and, to some extent, the other roads, from somewhere in the vicinity of the "robbery" and workings of Nos., 1 and 2 Brakes.
Indications of considerable fire were found at the Southern extremity of No. 1 Brake district, and another at the point towards the north-western corner of No. 2 Brake district (see plan II.) ; the sites of these fires, like the "friction-gear," representing places at or just beyond which the explosion had died out. No exact spot could be pointed to as that at which the explosion had originated. The expert witnesses were unanimously of the opinion that the explosion originated at some spot at or near the face, between the "Dilly" and the southern end of the district, and I agree with them in this conclusion.
Mr. Atkinson, for instance, puts forward as the most likely spot that in which the Reed's bodies were found (see Plan II.). Professor Galloway, on the other hand, advances reasons against this theory, and like him I cannot select any one particular spot in preference to others up the No. 1 Brake. There are strong evidences to my mind, that it may have occurred in the place named "Mather's place," for the reason of description, but I hesitate to advocate this in preference to other places, as there are contradictory evidences in each case. The fact is that the "back lash" succeeding an explosion destroys much of the evidence of an explosion by developing a force in a contrary direction to that of the explosion blast. The ignition may have taken place at any point and flashed across the goaf edge, the explosive force being developed at a distance of many feet away from the point of ignition. I have included, as Appendices to this Report, the statements prepared respectively by Messrs. Atkinson and Galloway, both are worthy of the most careful perusal, see Appendices A and B.
Mr. W. C. Blackett, a mining engineer of very great experience in colliery explosions, said he preferred not to say exactly where the ignition occurred. In answer to questions addressed to him by myself he said :
"It has been a very difficult colliery to find sufficient evidence in. There is such an absence of timber and absence of opportunities for violence to show itself, that it is not at all an easy occasion on which to read the thing, and therefore it is not so easy in this colliery with its splendid roof, to follow out as it had been on many occasions the exact points of ignition. And besides, in an occasion like this, where in all probability, as I think, gas had had a good deal to do with it, it is not like tracing up a shot where you find its exact point, and therefore I cannot fix upon a point quite definitely . . . . What I do think happened there, as the balance of probabilities, was that the roof of the goaf fell very heavily, and that forced out some gas, that, I have no doubt, would lodge in that goaf like it does in most cases, and also I have every belief that it would raise up at the same time a good deal of dust, and that it was not a pure firedamp explosion to begin with, but was a mixed-up firedamp and dust explosion. That it developed its violence in all directions from a point somewhere here (pointing to the neighbourhood of Mather's place and the place where Reed's bodies were found.) I cannot say definitely Reed's place. I cannot say definitely Mather's place, but it is somewhere in that neighbourhood. That developed as it did into an inflammation which naturally flung out the air before it in all directions. That was going North owing to its being able to open out into the greatest number of galleries would not stir up perhaps quite so much dust at any rate not confine itself into such a small boundary as it would going in this direction, so although we get dust igniting and spreading all over in this direction and coming down here."
"In a series of explosions "? — "No, not in a series of explosions but in a continued ignition which develops different phases of violence according to the conditions in which it found itself as it went on. Now going North it found itself more confined into this smaller set of galleries here. The air became more compressed in this direction and to get a very much more violent phase in the explosion in the end of this heavy goaf, although confined, than we did going in this direction. To my mind that accounts for the extraordinary violence exhibited on those tubs just at the end of this very heavy goaf."
"And on the release of that compression there would be considerable violence in the reverse direction "? — "On the release of that compression. If you had an explosion in this room and it blew out the windows and doors in all directions when the heated air contained in the room cooled and condensed it would necessarily blow in again to fill up the empty space."
As to the cause of the explosion there can be no doubt that it was initiated by the ignition of firedamp in the neighbourhood of the goaf.* This gas may have been driven out of the goaf with great force, due to heavy falls of stone, and it may have fired at a defective lamp — defective from injury through violence, or a cracked glass due to heat or violence. A tilted lamp would allow of the flame impinging on the glass and this might possibly crack it. Lamps were not suspended on stands at this colliery. (I myself during exploration work found lamps placed on the floor in close proximity to gas, acting as a danger signal, but the man who was supposed to be attending to them was further inbye.) Or the explosion may have been caused by matches left in the workings — one cannot say, one can only surmise.
The placing of the stoppings alluded to by me in this Report and by Professor Galloway in his statement would undoubtedly close a natural escape to the gas in the goaf. The roof, which was upstanding in the No. 1 brake area on the day of the explosion, was found to be heavily fallen when the district was re-entered. The roof, being so strong, would, on coming away, fall over a large area, and drive the collected gas out with a force almost equal to that of an explosion. It is doubtful whether any gauze safety lamps would withstand such an onset.** Or a lamp may have been burning in a gaseous mixture until the gauze became red hot, and so the lamp ceases to be a safety lamp. As to evidence afforded by the lamps, a safety lamp which had passed flame owing to the heating of the gauze would not necessarily present indications of violence. Lamps with cracked glasses may have had them broken by the explosion, and injuries of other kinds may have been caused by the lamps being hurled against obstructions or subjected to a hail of small stone and coal swept up by the explosion. The evidence afforded by lamps, therefore, is always of a doubtful nature on account of the violence which those in the area of force are subjected.
It will be observed that the explosive force did not go far into the return airways, a fact which may be accounted for by the comparative absence of coal dust in these roads. Further, the humidity of the air, would render such dust as there might be innocuous.
* The gas may have been in part or entirely derived from a seam of coal, under one foot in thickness, which existed a little depth below the Main Band, but which at the inbye edge of the goaf would be brought some little way above the Main Band level by the fault forming the Eastern boundary of the 3rd North District: this seam was noted for being very "gassy."
** Some of the lamps were tested at Leeds University in the presence of a representative of the management (Mr. Steele), of the men (Mr. Hanlon), and Mr. J. B. Atkinson and were subjected to an explosive mixture of gas and air having a velocity of 1,260 feet per minute. They, however, successfully withstood the test.
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